Event/escrow php project

Sort of a paypal/epay/escrow clone....a user registers their event and lets other users donate money using paypal to that event *user selects group when registers*. Admin charges percentage fee per money transfer from paypal. User can link to each event directly when they send emails. Will show how much money has been added to the event (minus admin fees). User can add as many events as they want. Event will have two images, a description portion, date, time, and comments section where other users can comment. Users can send emails and monitor who they've asked to donate based on who they've sent emails to, and who has sent money (based on email address).

Admin monitors all events, users, and donations. Script to use paypal ipn. Users can send money to other users just like escrow using paypal. Admin takes percentage of course..there is a limit on withdrawal.

I know 100 is in the middle range for something like this, but give me your best offer....I'm assuming you can adapt a ready-made escrow system for this project